Sophon

Thank for the info, that will come in handy. I have some 16 sq.mm. cable left over from the house construction, so I guess I could use that.

Thank you. One thing I am a little hazy about, are the actual connections on the DC side. From your picture it looks like there are special plugs for plugging into the inverter, rather than the "shove the cable into a hole and tighten a screw" that I am used to on the AC side. The same is probably true for the battery connections, and I have already seen that it's the case when connecting the solar panels. I am also not clear on what cable sizes I need for a 5 kW system, one of the sellers of inverters on Lazada quoted 4 sq.mm. but is that enough for a sustained energy flow of up to 5 kW? FWIW the finished cables that Global sell does seem to be mostly 4 sq.mm. And, as I have not presently any surge suppressors, what kind of cable sizes do they require? They need to be able to divert large amounts of energy, but obviously only for a very short time. Hopefully, these are things that will become clear with further research.

Thank you again Crossy. I will let you get back to enjoying your week-end.

This is where I feel completely lost, i.e. when trying to figure out if equipment meets my requirements or not. How do I know if these two examples of DC MCB's can be used for my battery storage, what is it in the description that gives it away? There are wiring diagrams on the MCB's themselves, but I don't know enough to understand them. Example 1: There are a couple of questions about polarity in the Q&A, but the translation makes them incomprehensible: Example 2:

Thanks. Stupid question alert! I assume that I can use the same ground bus bar for both the AC and DC (surge suppressors) side?

Hi again Crossy. In my reply to using a changeover switch for changing between essential/non-essential load in a hybrid on-grid system, you suggested maybe using one to bypass the inverter also in a hybrid off-grid system. Did you mean something like this: Any glaring mistakes in my diagram? I haven't yet added surge protection on the DC side, as I don't really know where it would be needed?

So that means that I can wire up an AC MCB either way, but what about the MCB for the battery storage? Does that mean that there are special MCB's specifically for the battery storage?

Stupid question. Are normal MCB's directional? In most wiring diagrammes I have seen they have input at the top of the MCB and output at the bottom like e.g. this one: Sometimes it would make for easier wiring to have the input on bottom, and when talking about the MCB for battery storage the energy can flow either way depending on the circumstances. I would have thought that MCB's are bi-directional, and can be wired up either way, but as we have already established my electrical knowledge is limited.

Yeah, I was aware of that. It seems that DC breakers and wiring in general is a little more expensive than AC equipment, but it will not be a major cost so not that important.

Sounds good that I can use a local ground rod, that will make my life easier. I will have string inverter(s). With 12 panels, I believe I would connect them as two strings each with six panels in series, and the two strings then connected in parallel? I am sorry, you lost me with the "and don't forget the D side", is "D" a specific type of arrestor or what did you mean by that?

I have snipped your post to highlight the relevant (to this post) part. Yeah, it's always difficult weighing up options when you are not sure what the future brings. I could do as you suggest, and buy two 5 kW hybrid off-grid inverters, so that i know they would be compatible. The down-side being that I may in reality only need one, so having wasted the cost of the second one. Alternatively, I could buy just one and hope that I can find a compatible unit (or the same model if not to much time has passed), if it turns out that one unit is insufficient. Of course, the risk being that I can not find a compatible unit, and have to buy two new ones, wasting the investment in the original one. The second option do have the benefit of giving me added flexibility. Assuming the first 5 kW hybrid Off-grid inverter lasts me a year or two, and during that time I decide that I need to change to a hybrid on-grid inverter, I would have wasted less money than if going for two inverters right away. Of course, since splitting my load is a deal-breaker the latter option of switching to on-grid would only work, if I can find an acceptable solution to the essential/non-essential load connections. Have you seen my question about connecting both output ports from a hybrid on-grid inverter to a manual switch-over switch, such as is normally used to switch between grid and generator? Could that work? It would give me the option to: Have the switch default on "essential load", and manually switch to "non-essential when I need more than the inverter can handle (when charging EV via wall charger), or have the switch default on "non-essential load", and manually switch to "essential" when power goes out. If i can find an acceptable option to the load problem with an hybrid on-grid inverter, I think that I will probably initially go with a cheap Chinese hybrid off-grid inverter like the model BritManToo uses. That way I can learn from my own real life experience, without having wasted too much on equipment that it may turn out doesn't deliver what I need. Thank you for your patience in answering my questions. I know some of them must sound basic (or even down-right stupid) to you.

From reading posts in the electrical forum over the years, I have learned that having more than one ground can in certain situations be extremely dangerous. As mentioned, my solar panels will be ground mounted close to where the incoming supply enters our land, which is about 50 m (as the crow flies) from the house and where the existing ground rod connected to the consumer unit is located. At the moment I don't have a supply isolation breaker (other than the main RCBO in the C.U), nor do I have any surge protection, so the only way to cut the supply is to have PEA pull the cable from the meter. This is an oversight I now plan to fix, so I will put an incoming breaker where the PEA cable is today crimped onto my cable running to the house and after that I will add a MOV (I think it's called?) surge protection unit. These will be in a small box on the pole we had erected to receive our incoming supply from the PEA pole, which is on the other side of the soi. the new box will be here, where the workers plugged in their equipment during the construction of the house (looks safe, doesn't it?). The panels will be located a few meters away from this pole, and the inverter and battery etc. will be under the panels protected from the elements with some walls (but semi open for ventilation). The Inverter, as well as the surge protection I plan to add, will both need to be grounded, and as the existing ground rod is 50 m away it would not be very practical to run cables to it if it can be avoided. So would adding a second ground rod next to the panel location create a dangerous situation? I have also read about people using the house roof construction as a UFER ground, so would the 6 m x 4 m metal structure with six concrete footers I will build be a suitable ground and would you connect the inverter/surge protection to the structure as well as the second ground rod? All that is, of course, assuming that the answer to my first question is, that a second ground rod 50 m from the existing one will be OK.

Thanks for your comments and suggestions Crossy. Our incoming supply goes from the PEA pole to a pole at the corner of our land (where the solar panels would be located). It then goes underground for 50+ meters and enters the house through the wall downstairs: From there it goes through the floor of the living space upstairs into a cavity wall of one of the upstairs bathrooms into the ceiling space. Making that whole in the wire mesh reinforced concrete floor was a major task even back when the cavity wall was not there yet. It then comes down to the consumer unit embedded in the AAC wall: Splitting the load into essential and non-essential, would require me to run a second buried cable to the house (in itself an added cost of THB 20k+). I would also have to drill extra holes in the downstairs wall, the floor between downstairs and upstairs, embed the extra cables and a second C.U. in the wall . After that I would have to have the wall upstairs and the ceiling downstairs re-plastered and the downstairs wall re-tiled. That is in addition to the actual re-wiring work, which would require me to extend at least some of the existing cables. Having to split the load would be an absolute deal-breaker for me. I have some questions about grounding that I would like your input on, but I think I will post those in a separate post.

With what I have so far learned, i am thinking that the hybrid on-grid system is probably not worth the extra cost, so I am now leaning towards going for a 5 kW hybrid off-grid inverter. If it turns out to be insufficient, especially if i later install a 7 kW wall charger for the EV, I can add a second inverter (I know not all inverter models can do this). Still a little confused though, as Crossy states this about the hybrid off-grid system in his pinned topic: But I am pretty sure that I have read a post from Crossy in a separate topic, where he mentions a model of hybrid off-grid inverter that is able to top up from the grid to deliver more than the inverters rated capacity (and BritManToo saying that his Chinese model can do the same). So some hybrid off-grid inverters do have the ability to top up from the grid???

I looked up the website of the company that are doing the project down at our local river, and found these prices (seems to be without battery storage) Quite pricy.

I don't really care whether the panels are blue or black, to be honest the lack of symmetry if having 9 panels mounted in two rows would bother me more. Following your link, I can not find all your panels at your quoted prices. However, I did find this additional 340 w panel on sale: link. I think Crossy have previously bought that panel. I assume your 410 w panel is this one. link The only 450 w panel I could find is this one, but the price is lower than you quoted link The slight problem with the higher rated panels is, that they are slightly bigger and heavier. The metal for my structure comes in lengths of 6 m, so with the 340 w panels being 99 cm x 196 cm they fit neatly with two rows of 6 panels. The 450 w panels are 104 cm x 210 cm, so would not fit as neatly. But that's just a slight niggle, it will not be the deciding factor. I have seen Crossy say several times that if there is no limitations on mounting space, he would go for the most watt per Baht. With the 340 w JinYuan panels on sale, that would at this time make them the best value for money at THB 41,880 for 12. I really appreciate you taking the time to dig up and post information for me.

No, I am not sure that 12 panels is enough but I believe they probably will be. If it turns out it's not enough I can always add more later. With your own estimates of 75% efficiency and 6 hours of sunlight per day and 12 pcs 340 W panels, I make it a production of 340*12*.75*6 = 18 kWh on an average day. Our consumption over the last several years have been between 11-12 kWh per day, so well below the average expected 18 kWh output from the panels. When we get our new EV, our consumption will probably increase by about 3 kWh per day, so still below the 18 kWh/day. I appreciate that averages are just that - averages. There will be days when we use more than our normal 11-12 kWh, and there will be days when the panels produce less than the average 18 kWh. Most days the panels should be able to cover our consumption, and on days where they are not, well that's what PEA is there for. Please don't apologize for giving information I may already be aware of. As I am a new to this there is a good chance the information you give is something I don't already know. And even if I did know something already, it's always good to have information reinforced and it could also be of benefit to other people.

Because the inverter will be located 50 m from the house, so it would require a second buried cable as well as a major rewiring of the house. As I mentioned before, I wouldn't generally charge from the mains as that would be counterproductive, but maintaining a small charge to give UPS functionality could possibly be helpful. I am just in information gathering mode at the moment, trying to ascertain what is possible and what is not. Then a few months down the line when i am ready to go, I will be better equipped to decide how to design the system.

I obviously don't want to have the power go out, an important part of the project is to avoid that. A 5 kW inverter would easily supply my whole house, the only thing I would have to avoid is charging the EV, especially if I in the future install a 7 kW home wall box.. What I would like to achieve is: When PEA power is on, I want to supply the whole house and also have the ability to go above the 5 kW inverter limit (when charging the EV). When PEA power is off, I still want to supply the whole house, but will manually take care not to use the most power hungry utilities (i.e. EV charging) to avoid exceeding the inverter limit. But how would I connect the house load to the inverter. I assume that there must always be power going to the essential output port, but that it is limited to 5 kW. The non essential output port can go above the inverter limit, but will have no power when the grid is out, is that correct? So would I need to connect both ports to a changeover switch like this one (and would that work)?: default would be keeping the switch to take input from the essential load port limiting me to 5 kW power, and switching it over to take input from the general power load port when I need more than 5 kW and know that the grid is active. Would that work, and is there a more elegant solution? What would happen if both output ports were connected to the house load at the same time, without a changeover switch, would something go poof?

That sounds good. I don't foresee a situation where I would exceed 5 kW anyway, but I guess that it would be possible for the grid to be out when there is no sun and I have also run out of battery charge.

OK, so what I call an inverter is actually all the elements within the dotted line, of which the actual DC to AC inverter is just one element. So I "just" have to set up the unit in a way that suits my needs. I did say, that I had probably misunderstood something. I realize that this may work differently between different models, but can the "inverter" be set up so that it only charges from the mains if the battery falls below a certain level of charge? With regards to the essential load, can I connect the whole house to both the normal load port and to the essential load port. I assume (I know, dangerous) that the essential port is limited to the maximum power of the inverter, so I won't be able to just connect the whole house to the essential port? I don't want to split my circuits into two groups. Thank you for your explanation.

Something I have been wondering. In a hybrid on/off grid system, what happens if the grid is off and the house load exceeds the capacity of the inverter? Will the voltage drop, or how will the lack of power manifest itself?

I will keep that in mind. I guess that even a fairly weak signal will probably be OK, as the amount of data being exchanged must be quite small so slow speed should still work.

That's scary. and one of the opponents being a retired science teacher no less. Crossy, have you seen my questions from yesterday about the illustration in your pinned topic about different solar installation types? I would love to have your comments, when you can find the time.

The installation down by Tha river with the panels mounted (but nothing connected). They are 450 W panels, so with a total of 84 panels that's quite a bit of potential energy being produced.